Hydraulic dockboard system

Abstract

A hydraulic operating system for a series of dockboards mounted on a loading dock. Each dockboard includes a hydraulic cylinder unit that is employed to elevate the ramp, and a single hydraulic pump unit is utilized for the series of dockboards. A discharge line is connected to the outlet of the pump unit, while a return line connects the inlet of the pump to a reservoir, and individual supply lines are connected to the hydraulic cylinder units of each dockboard. A multiple position valve interconnects the discharge line, the return line and the supply lines and is operable to selectively direct hydraulic fluid through the discharge line to at least one of said supply lines to operate the corresponding cylinder unit and elevate the ramp of that dockboard, and for simultaneously connecting the other supply lines to the return line.

I claim: 
     
       1. A dock loading system, comprising a dock, a plurality of dockboards mounted on the dock, each dockboard including a supporting structure and a ramp hinged at its rear edge to the supporting structure and movable between a generally horizontal cross traffic position and an upwardly inclined position, each dockboard also including a hydraulic power unit connected between the supporting structure and the ramp for raising the ramp from the horizontal position to the upwardly inclined position, a discharge line, hydraulic pumping means connected to said discharge line for maintaining a substantially constant pressure in said discharge line, a return line connected to the inlet of the pumping means, a supply line connected to each power unit, and valve means operably interconnecting the discharge line, the return line, and the supply lines for selectively directing fluid from the discharge line through at least one of said supply lines to the corresponding power unit to thereby raise the ramp of the corresponding dockboard and for simultaneously connecting the other supply lines to the return line. 
     
     
       2. The system of claim 1, wherein said dockboards are arranged in groups with each group including at least two dockboards, said system including valve means for each group of dockboards and a branch line connecting the discharge line to each valve means. 
     
     
       3. The system of claim 2, and including flow control means in each branch line to control the rate of flow of hydraulic fluid from the discharge line to the respective valve means. 
     
     
       4. A hydraulic dock loading system, comprising a loading dock having a plurality of pits therein, a dockboard mounted in each pit with each dockboard including a supporting structure, a ramp hinged at its rear edge to the supporting structure and movable between a generally horizontal position and an upwardly inclined position, each dockboard including a hydraulic cylinder unit connected between the supporting structure and the ramp for raising the ramp from the horizontal position to the upwardly inclined position, said dockboards being arranged in a series of groups with each group comprising at least two dockboards, hydraulic pumping means, a discharge line for each group of dockboards and connected to the outlet of said pumping means, means for maintaining a substantially constant pressure in each discharge line, a return line for each group of dockboards and connected to the inlet of the pumping means, a supply line connected to the cylinder unit of each dockboard, valve means for each group of dockboards and operably interconnecting the discharge line and the return line and the supply line of that group for selectively directing fluid from the discharge line to at least one of said supply lines to raise the ramp of the corresponding dockboard and for simultaneously connecting the other supply lines of that group to the corresponding return line so that the ramps of the corresponding dockboards are free to float up and down. 
     
     
       5. The system of claim 4, and including flow control means in each discharge line to control the rate of flow of fluid through the respective discharge line whereby the flow through each discharge line constitutes only a portion of the total rate of flow of the pumping means. 
     
     
       6. A hydraulic dock loading system, comprising a loading dock having a plurality of pits therein, a dockboard mounted in each pit with each dockboard including a supporting structure, a ramp hinged at its rear edge to the supporting structure and movable between a generally horizontal position and an upwardly inclined position, each dockboard including a hydraulic cylinder unit connected between the supporting structure and the ramp for raising the ramp from the horizontal position to the upwardly inclined position, said dockboards arranged in a series of groups with each group comprising a pair of dockboards, a single hydraulic pumping means, a reservoir connected to the inlet of said pumping means, a discharge line for each group of dockboards and connected to the outlet of the pumping means, said pumping means being operable to maintain a substantially constant pressure in said discharge lines, a return line for each group of dockboards and connected to the reservoir, a supply line connected to the cylinder unit of each dockboard, valve means for each group of dockboards and operably connecting the discharge line, the return line and the supply lines of that group, each valve means having a first position wherein the supply lines are connected to the return line whereby the ramps can float freely up and down during a loading operation, and having a second position wherein a first of said supply lines is connected to the discharge line and a second of said supply lines is connected to the return line whereby fluid is supplied to the cylinder unit associated with said first supply line to thereby elevate the corresponding ramp and the ramp associated with the second supply line is free to float and having a third position wherein said second supply line is connected to the discharge line and said first supply line is connected to the return line whereby fluid is supplied to the cylinder unit associated with said second supply line to thereby elevate the corresponding ramp and the ramp associated with the first supply line is free to float, and means for moving said valve means between said positions. 
     
     
       7. The system of claim 6, and including flow control means in each discharge line to control the rate of flow of fluid through the respective discharge line whereby the flow through each discharge line constitutes only a portion of the total rate of flow of the pumping means. 
     
     
       8. The system of claim 6, and including means for maintaining a substantially constant pressure in each discharge line.